Quaternary ammonium halides can be prepared according to known methods by reacting tertiary amines with alkyl halides. This reaction is generally carried out in polar solvents, preferably in water, ethanol, isopropanol, or a mixture thereof. It is necessary to use considerable quantities of solvents, especially in the preparation of quaternary ammonium halides having longer chain alkyl radicals, since these compounds have only a limited solubility and their concentrated solutions have the undesirable property of forming a gel. The upper concentration limit of quaternary ammonium halides in solution is thus, in practice, about 50% by weight; however, in many cases, it is necessary to work with concentrations of 20% by weight or less.
If large quantities of solvent are used, the capacity of the reaction vessels is not fully utilized. Also, if the quaternary ammonium halides thus produced are recovered from the solvent by evaporation, then additional energy has been expended. Further, when the products are used in the form which they are obtained, namely, as solutions, additional expenditures for transportation are oftentimes required.
It has been surprisingly discovered that quaternary ammonium halides can be obtained in a simple manner, free from solvents, and in finely-divided form.